1. Field of the Invention
The present invention relates to cellular radio communication networks, and particularly the handover of mobile user equipment units (UEs) from one routing area to another.
2. Related Art and Other Considerations
Cellular telecommunications systems employ a wireless link (e.g., air interface) between a (mobile) user equipment unit (UE) and a base station (BS) node. The base station node has transmitters and receivers for radio connections with numerous user equipment units. One or more base station nodes are connected (e.g., by landlines or microwave) and managed by a radio network controller node (also known in some networks as a base station controller [BSC]). The radio network controller node is, in turn, connected through control nodes to a core communications network. Control nodes can take various forms, depending on the types of services or networks to which the control nodes are connected. For connection to connection-oriented, switched circuit networks such as PSTN and/or ISDN, the control node can be a mobile switching center (MSC). For connecting to packet switching data services such as the Internet (for example), the control node can be a gateway data support node through which connection is made to the wired data networks, and perhaps one or more serving nodes.
A radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by a unique identity, which is broadcast in the cell.
One example of a radio access network is the Universal Mobile Telecommunications (UMTS) Terrestrial Radio Access Network (UTRAN). The UTRAN is a third generation system which in some respects builds upon the radio access technology known as Global System for Mobile communications (GSM) developed in Europe. UTRAN is essentially a wideband code division multiple access (W-CDMA) system. The Universal Mobile Telecommunications (UMTS) Terrestrial Radio Access Network (UTRAN) accommodates both circuit switched and packet switched connections. In this regard, in UTRAN the circuit switched connections involve a radio network controller (RNC) communicating with a mobile switching center (MSC), which in turn is connected to a connection-oriented, external core network, which may be (for example) the Public Switched Telephone Network (PSTN) and/or the Integrated Services Digital Network (ISDN). On the other hand, in UTRAN the packet switched connections involve the radio network controller communicating with a Serving GPRS Support Node (SGSN) which in turn is connected through a backbone network and a Gateway GPRS support node (GGSN) to packet-switched networks (e.g., the Internet, X.25 external networks).
Cellular radio communication systems use a functionality called handover to continue established calls when the mobile user equipment unit moves between different cells in the radio access network. The concept of handover is discussed, at least in part, e.g., in U.S. patent application Ser. No. 09/035,821 for “Telecommunications Inter-Exchange Measurement Transfer,” and U.S. patent application Ser. No. 09/035,788 for “Telecommunications Inter-Exchange Congestion Control,” both of which are incorporated herein by reference.
In order to support low activity UEs with a low utilization of the radio resources, a concept of UTRAN routing area (URA) and routing area update (URA update) has been introduced in UMTS. A UTRAN routing area (URA) is a geographical area comprising one or more cells. Each URA is identified by a unique identifier, which is broadcast in all cells belonging to the URA. A URA can comprise cells controlled by more than one radio network controller (RNC). In this regard, a URA with cells in more than one radio network controller (RNC) is referred to as an overlapping URA.
User equipment units that are having low activity (no user data transfer) at the moment may switch to a “URA Connected” state. When in “URA Connected” state the user equipment unit will only report change in its location when moving from one URA to another. The present invention is intended for, but not limited to, cellular networks, where the existence of URAs or equivalent allows the user equipment unit to remain “connected” with the network in a low activity state utilizing a minimum of radio interface resources.